Seismology of transversely oscillating coronal loops with siphon flows

TL;DR

This paper develops a theoretical model for the frequency of standing kink oscillations in coronal loops with siphon flows, revealing how flows affect wave properties and magnetic field estimations in the solar atmosphere.

Contribution

It introduces a new expression for kink mode frequency accounting for siphon flows, applicable across different flow speed regimes, and demonstrates its use in solar coronal seismology.

Findings

Siphon flow causes a linear phase shift along coronal loops.

Flow introduces asymmetry in eigenfunctions of oscillations.

Flow presence can lead to underestimation of magnetic field strength.

Abstract

There are ubiquitous flows observed in the solar atmosphere of sub-Alfv\'{e}nic speeds, however after flaring and coronal mass ejection events flows can become Alfv\'{e}nic. In this Letter, we derive an expression for the standing kink mode frequency due to siphon flow in coronal loops, valid for both low and high speed regimes. It is found that siphon flow introduces a linear spatially dependent phase shift along coronal loops and asymmetric eigenfunctions. We demonstrate how this theory can be used to determine the kink and flow speed of oscillating coronal loops with reference to an observational case study. It is shown that the presence of siphon flow can cause the underestimation of magnetic field strength in coronal loops using the traditional seismological methods.